The present invention is directed to a current controlled, linearly variable inductor. More specifically, the present invention relates to a magnetically saturating inductor having a variable inductance controlled by the application of a direct current.
Currently known inductors, transformers, and reactors incorporating magnetically saturable cores have several disadvantages. These disadvantages include a low inductive energy density relative to the core size, a low range of tunable inductance relative to the bias control current required, high core losses relative to the amount of energy stored, non-linear response, and a narrow range of operating frequencies. The high core losses also cause corresponding distortion of applied voltage waveforms.
An example of saturable core reactor construction is described in U.S. Pat. No. 4,766,365, which teaches a "EE" or three-limbed magnetically saturable core having air gaps on two outer limbs. In this configuration, magnetic energy may flow either through the core material or across the air gaps. Energy loss occurs in the core material in proportion to the flux energy that is converted to heat, and also in proportion to the flux energy that is coupled to conductors outside the core due to fringing of the flux across the air gaps. Unless otherwise noted, all references to flux mean magnetic flux. Fringing may be reduced by enlarging the cross section of the limbs in relation to the width of the air gaps, but this approach further increases the size and weight of the core.
In view of the disadvantages noted above, a need exists for a magnetically saturable inductor having a higher inductive energy density relative to the core size, a higher range of tunable inductance relative to the bias control current required, lower core losses relative to the amount of energy stored, a linear response, and a wider range of operating frequencies.